1. Field of the Invention
The present invention relates generally to a method of manufacturing a motor and more specifically to a process of manufacturing a motor body including a magnetized motor magnet for a DC motor, for instance.
2. Description of the Prior Art
As is well known, DC motors are used in various industrial fields. In the DC motor, the motor body or motor housing made of a synthetic resin, for instance, is usually provided with a magnetized motor magnet, and a motor rotor including a motor coil is housed within the motor body so as to magnetically react with the motor magnet when current is passed through the motor coil by the aid of a pair of brushes attached to the motor body and a commutator attached to the motor rotor. In order to increase the energy transduction efficiency of the motor, it is preferable to reduce the clearance between the inner circumference of the magnet and the outer circumference of the rotor as much as possible and to such an extent that both the elements are not in contact with each other.
In a prior-art method of manufacturing the motor body including a magnet, a magnet is first fitted to a cylindrical portion of a molding core; secondly, the core having the magnet is inserted into a hollow cavity of a mold so as to form a cup-shaped space between the mold and the core having the magnet; thirdly, a resin material is injected into the cup-shaped space to form a motor body; fourthly, the core is extracted from the mold together with the magnet and the motor body, and the core is further extracted from the magnet and the motor body.
In the prior-art method as described above, however, there still exist several problems as follows: since the magnet should be magnetized before the molding of the motor body and further that the magnetized magnet should be fitted one by one to the molding core, the magnet should be manufactured accurately in dimensions and furthermore should previously be stocked before molding the motor body. That is to say, the prior-art method requires troublesome labor and is costly, thus being not well applicable to the mass-production process.
The prior-art method of manufacturing a motor body or a motor will be described in more detail hereinafter with reference to the attached drawings under Detailed Description of the Preferred Embodiments.